1. Field of the Invention
The field of the present invention relates to a mobile classifier (deduster) with docking devices, flushing devices and control for the dedusting of granules, in particular polymer granules, with preference polycarbonate granules. Such a mobile classifier can be set up at different locations underneath silos. To perform its function, the mobile classifier is technically connected to stationary pipelines, filters and fans.
2. Background
The granular product occurring in the reactor during the production of thermoplastics is plasticated in an extruder and formed into individual strands, which are cut into granules by means of a knife rotating in the granulating die. The granulation may be performed, for example, in a stream of liquid. Subsequently, the granules are dried and screened, in order to separate out agglomerates formed in spite of cooling. After that, the product is pneumatically conveyed to a mixing silo, from which the product is then filled and packaged. On account of the silo design and the filling strategy, mixing (homogenization) of the product inevitably takes place when it is removed from the mixing silo.
In order to separate out abraded material in dust form and further materials in dust form that are formed during the pneumatic conveyance or during mixing, depending on the proportion of dust, the granules are subjected prior to the filling or packaging process to a dedusting operation performed by air classification by means of a classifier (deduster).
Classifiers are known per se and are described, for example, in U.S. Pat. No. 5,035,331, U.S. Pat. No. 6,595,369, U.S. Pat. No. 7,380,670 and U.S. Pat. No. 7,621,975. However, these disclosures are merely concerned with increasing the efficiency of stationary classifiers (better dedusting) and ignore the handling of the classifier itself, and possibly the suitability thereof for being washed down to avoid contamination by dust and granules from an earlier dedusting operation involving different granules, which contaminate the present product during the dedusting in the classifier.